Process for producing low-pilling textile fiber

ABSTRACT

METHOD OF SPINNING LOW I.V. POLYETHYLENE TEREPHTHALATE FIBER COMPRISING ADDING ALUMINA TRIHYDRATE TO POLYMER HAVING AN I.V. OF ABOUT 0.50 TO 0.65 AND PROGRESSIVELY INCREASING THE TEMPERATURE OF THE POLYMER DURING SPINNING TO DEHYDRATE THE ALUMINA TRIHYDRATE AND REDUCE THE I.V. OF THE POLYMER BY HYDROLYTIC DEGRADATION. ALSO DISCLOSED IS THE PROCESS BY WHICH THE LOW I.V. FIBER CAN BE PROCESSED TO PRODUCE A FIBER WHICH HAS LOW-PILLING CHARACTERISTICS

United States Patent 3,808,302 PROCESS FOR PRODUCING LOW-FILLING TEXTILEFIBER Richard F. Dyer, Kingsport, and August K. Meyer, Blountville,Tenn.; said Meyer assignor to Eastman Kodak Company, Rochester, NY. NoDrawing. Filed Oct. 25, 1972, Ser. No. 300,638 Int. Cl. D01f 1/02; C08g51/04 US. Cl. 264211 4 Claims ABSTRACT OF THE DISCLOSURE Method ofspinning low I.V. polyethylene terephthalate fiber comprising addingalumina trihydrate to polymer having an I.V. of about 0.50 to 0.65 andprogressively increasing the temperature of the polymer during spinningto dehydrate the alumina trihydrate and reduce the I.V. of the polymerby hydrolytic degradation. Also disclosed is the process by which thelow I.V. fiber can be processed to produce a fiber which has low-pillingcharacteristics.

This invention relates to a pill resistant poly(ethylene terephthalate)fiber and a process for producing the fiber. The poly(ethyleneterephthalate) textile fiber is characterized by an inherent viscosityof about 0.370 to 0.40, ultimate tenactity of about 2.6 to 3.2 grams/denier and elongation of about 25-40%.

The fiber is produced by incorporating alumina trihydrate in fiber gradepoly(ethylene terephthalate) polymer and controlling the spinning andprocess conditions in a specific manner to produce the pill resistantfiber.

Poly(ethylene terephthalate) fibers, the preparation of which isdescribed in US. Pat. 2,465,319, are widely used in the preparation offabrics characterized by ease-of-care properties associated with fastdrying, crease recovery, and wrinkle resistance as well as strength andabrasion resistance. However, the use of poly(ethylene terephthalate)stapel fiber for certain end uses has been restricted by a phenomenonknown as pilling, which refers to the accumulation on the surface of thefabric of numerous unsightly small balls of fiber, sometimes with theinclusion of foreign material. It was early recognized that theunsightly effect of pilling was not due so much to the formation ofpills, which occurs in all fabrics prepared from staple fibers, but tothe difficulty in wearing off the pills once formed, since the strengthand abrasion resistance of poly(ethylene terephthalate) prevents theirrapid removal during normal use of the fabrics.

Many attempts have been made to modify the poly (ethylene terephthalate)fiber itself in order to inhibit the tendency toward pilling in fabricscontaining the staple fiber. One of the solutions to the problem hasbeen to prepare the fiber from polymers of relatively low molecularweight, characterized by sharply reduced viscosity values.Unfortunately, in attempting to reduce the viscosity of the spunpoly(ethylene terephthalate), it has been found that the difficulty inspinning the polymer rapidly increases as the viscosity is reduced. Thechief problems encountered when the melt viscosity is low aremaintenance of the uniformity of the product and continuity of spinningof the molten filaments without the formation of drips. Most extrudersused for commercial production of polyester fibers are designed forpolyester resins having an inherent viscosity of 0.50 to 0.70 and aresultant high melt viscosity. When low I.V., low melt viscositypolymers are extruded, these extruders do not feed and control well andthe pressure of the melt delivered to the metering pumps is quitevariable. Engineering design considerations indicate that it would bedifficult to achieve enough energy input in a screw to melt the low I.V.polymer but still retain a high melt viscosity for uniform metering andpressure control. This is an undesirable situation and suggests the needfor a means other than low I.V. polymer for producing low pill polyesterfiber.

The inherent viscosity of polymers or fibers, referred to in thisspecification, is determined at 25 C. using a solution containing 0.23grams of polymer or fiber dissolved in 100 milliliters of a 60:40mixture of phenol-tetrachloroethane.

The process of this invention for producing a pill resistantpoly(ethylene terephthalate) textile fiber, comprises feeding to aspinning machine fiber grade poly(ethylene terephthalate) polymer havingan inherent viscosity of about 0.55 to 0.65, and about 0.20% to 0.35% byweight of alumina trihydrate; heating the polymer and alumina trihydrateduring its passage through the extruder barrel of the spinning machineto a temperature suificient to cause the release of a major portion ofthe available water in the alumina trihydrate and thereby reduce theinherent viscosity of said polymer by hydrolytic degradation; coolingsaid polymer at the spinning orifice about 30 C. or more; forming andtaking up the poly(ethylene terephthalate) fiber. The low I.V. fiberproduce is preferably processed by feeding the fiber through a waterbath heated to about C. at a speed of about m./m. with minimum snubbing;drafting the fiber about 2.5 :1; passing the fiber through a steamatmosphere heated to about C. while subjecting the fiber to a drafttension of about 0.5 gram/ denier; and heat setting the fiber for aboutfive minutes at a temperature of about C. The fiber made by the processis a pill resistant textile fiber of poly (ethylene terephthalate), thefiber having an inherent viscosity of about 0.370 to 0.40, fibertoughness of about 0.7 to 0.8 gram/denier, ultimate tenacity of about2.6 to 3.2 grams/denier, and elongation of about 2540%.

We have found that normal I.V. polymer with specified amounts of aluminatrihydrate added can be extruded with good extruder pressure controlbecause the temperatures along the extruder barrel and in the spin blockand spinneret can be controlled such that the release of water from thealumina trihydrate takes place at the end of the extruder barrel and inthe spin block. The alumina trihydrate releases its water at the desiredzone in the extruder barrel due to the temperature control of the barreland the water causes a breakdown of the I.V. of the polymer at the endof the extruder and in the spin block. In order to raise the meltviscosity of the polymer it is cooled at the spinneret at least about 30C. to aid in forming the fibers.

The alumina trihydrate may be added to the polymer by means of aconcentrate. For example, alumina trihydrate (1 micron diameter) may beblended into 0.60 I.V. poly (ethylene terephthalate) powder in a mixersuch as a Prodex Henschel mixer to form a concentrate containing 5%alumina trihydrate. The concenfrate is then added to 0.60 I.V. polymerin a rotary dryer, such as a Patterson rotary dryer, to form polymerblends which contain from 0.20% to 0.35% alumina trihydrate. Likewise,these blends could be made using alumina trihydrate of differentparticle size (for example 20 micron diameter) and could be added topolymers having an I.V. ranging from 0.50 to 0.65.

The amount of alumina trihydrate added to the polymer may be determinedby using the following equation:

where The fibers of our invention after being spun are processed in thefollowing manner to obtain the novel properties. The fibers are fed toconventional two stage drafting processing equipment similar to thatshown in US. Pat. 3,481,012. The preferred processing conditions are asfollows:

Water bath temperature, C 69 First stage draft ratio 2.5:1 Steam tubetemperature, C 150 Draft tension, grams/ denier 0.55 Draft speed, m./m.115-135 Heatset time, minutes Heatset temperature, C. 170

We have found that the low pill fibers of this invention made fromnormal I.V. polymer plus alumina trihydrate have a higher tenacity,about 2.6 to 3.2 grams/ denier, than prior art low pill fibers made fromlow I.V. starting polymers. This is one advantage of our novel fibersince finer cotton count yarn can be spun from the higher tenacityfibers than with prior art low pill fibers.

The following examples illustrate preferred embodiments of the inventionand illustrate processes similar to that of the invention but which donot result in low-pilling fibers. The examples illustrating theprocesses which do not produce low pilling fibers will be designated ascomparative examples.

EXAMPLE 1 Polyethylene terephthalate polymer containing 0.3% aluminatrihydrate of 1,11. mean diameter and having an inherent viscosity of0.60 is spun through a spinneret containing 33 2 holes of 0.55 mm.diameter at a melt temperature of 262 C. and wind up speed of 1000meters per minute. The extruder barrel temperature profile is 293, 305,295 and 285 C. on Zones 1, 2, 3 and 4 of the barrel respectively; Zone=1 being the feed zone. Extruder pressure control is acceptable and thefilaments thus obtained have an inherent viscosity of 0.38 and containno defects such as fused clusters, oversized filaments, and slubs whichare present in filaments spun from 0.40-0.42 I.V. polyethyleneterephthalate polymer because of poor extruder control (insufiicientmelt viscosity). These filaments are stretched with essentially nosnubbing in water heated to 68 C. at a draw ratio of 2.5 :1 (filamentsdrafted with snubbing produce fallout in carding, etc.) then stretchedfurther in 150 C. super heated steam at a ratio which produces a tensionof 0.55 g./d. The drawn filaments are then crimped in a stuffer boxcrimper, heat treated in 170 C. air for 5 minutes and cut into staplefiber. The physical properties of the resultant staple fiber are:

Denier per filament 3.3 Tensile strength g./d 2.9 Elongation at breakpercent 33 The staple fiber is carded and spun into polyester 24/ 18,3.5 T.M.Z. spun yarns on conventional equipment and knit into a fabricof double knit construction in a Ponte-di-Roma stitch on an 18 gaugecircular knititng machine. The knit fabric is pressure beck dyed 1 hourin a dye bath at 121 C. containing Percent Polyester carrier 4.0Penetrating agent 2.0 Anionic leveling agent 2.0 Sequestrant agent 1.0Eastman Polyester Blue BLF 2.7 Eastman Polyester Yellow W 2.7 EastmanViolet R 4.0 Eastman Polyester Red FFBL 0.9

and having a pH of 5.0 obtained by addition of acetic acid. The fiber tobath ratio is 3.0: l. The dyed fabric is secured, rinsed, extracted,slit and heatset at 350 F. using a 15% overfeed. Random Tumble PillingTest (ASTM D 1375- 64) measurements on this fabric give an index orrating of 4.25. A pill rating of 5.0 indicates no pills present and apill rating of '1.0 means an abundance of pills on the fabric.

EXAMPLE 2. COMPARATIVE EXAMPLE Spun filaments from Example 1 arestretched with essentially no snubbing in 68 C. water at a draw ratio of2.5:1 then further stretched in C. super heated steam at a ratio whichproduces a tension of 1.15 g./d. The physical properties of theresultant staple fiber are:

Denier per filament 3.1 Tensile strength g./d 3.1 Elongation at breakpercent 22 The drawn filaments are crimped and cut into staple fiber,processed into spun yarns, knit into fabric, dyed and tested for pillingin the manner described in Example 1. Random Tumble Pilling Testmeasurements on this fabric give an index or rating of only 2.0.

EXAMPLE 3COMPARATIVE EXAMPLE Polyethylene terephthalate polymercontaining 0.25% alumina trihydrate of 1,44 mean diameter and having aninherent viscosity of 0.60 is spun through a spinneret containing 510holes of 0.45 mm. diameter at a melt temperature of 270 C. and wind upspeed of 1200 meters/minute. The extruder barrel temperature profile is275, 285, 285 and 280 on Zones 1, 2, 3 and 4 of the barrel respectively;Zone 1 being the feed zone. Extruder pressure control is good and theinherent viscosity of the resultant filaments is 0.42. These filamentsare stretched with minimal snubbing in water heated to 65 C. at a drawratio of 1.6:1 then further stretched in 125 C. super heated steam at aratio which produces a tension of 0.6 g./d., crimped, heatset C. for 5minutes and cut into staple fiber. The physical properties of theresultant staple fiber are Denier per filament 3.0 Tensile strength g./d2.6 Elongation at break percent 30 The staple fiber is processed intospun yarns, knit into fabrics, dyed and tested for pilling using thesame procedure used in Example 1. The Random Tumble Pilling Testmeasurements on this fabric give an index or rating of 2.0.

EXAMPLE 4 and dyed using identical conditions to those used inExample 1. Random Tumble Pilling Test measurements on the resultantfabric would give an index of about 4.5 or essentially no pilling wouldoccur.

EXAMPLE 5 Polyethylene terephthalate polymer having an I.V. of 0.65 andcontaining 0.35% alumina trihydrate of 1 mean diameter is spun usingidentical conditions to those used in Example 1. Extruder pressurecontrol is good and the resultant filaments obtained will have an I.V.of 0.38. The filaments are stretched in the same manner as in Example 1and cut into staple fiber. The staple fiber is processed into yarns,knit into fabrics and dyed as in Example 1. Random Tumble Pilling Testmeasurements on the resultant fabric would give an index of about 4.5 oressentially no pilling would occur.

EXAMPLE 6.COMPARATIVE EXAMPLE Polyethylene terephthalate polymer havingan I.V. of 0.60 is spun through a spinneret having 510 holes of 0.45 mm.diameter at a melt temperature of 300 C. and wind up speed of 1100meters per minute. The extruder barrel temperature profile is 300 C. onall four zones. Extruder pressure control is excellent and the filamentsthus obtained have an inherent viscosity of 0.57 and contain no defects.These filaments are stretched with snubbing in water heated to 72 C. ata draw ratio of 3.0:1 then further stretched in 150 C. super heatedsteam at a ratio which produces a tension of 1.5 g./d. The drawnfilaments are then crimped in a stuffer box crimper, heat treated in 140C. air for 5 minutes and cut into staple fiber. The physical propertiesof the resultant staple fiber are:

Denier per filament 3.1 Tensile strength g./d 5.2 Elongation at break"percent" 41 The staple fiber is processed into spun yarns, knit intofabrics, dyed and tested for pilling in the same manner as in Example 1.The Random Tumble Pilling Test measurements on this fabric give an indexof 1.0.

Although the invention has been described in considerable detail withparticular reference to certain preferred embodiments thereof,variations and modifications may 6 where x=wt. fraction of aluminatrihydrate; y=wt. fraction of water of hydration of the aluminatrihydrate; I.V. =starting polymer I.V.; I.V. =desired fiber I.V.;t=residence time in extruder in minutes; T=melt temperature, K; andexp=base of natural logarithm.

(b) heating said polymer and alumina trihydrate during its passagethrough the extruder barrel of the spinning machine to a temperaturesufiicieut to dehydrate said alumina trihydrate and thereby reduce theinherent viscosity of said polymer by hydrolytic degradation;

(c) cooling said polymer before spinning about 30 C. or more; and

(d) forming and taking up said fiber.

2. Process of claim 1 wherein said starting polymer has an inherentviscosity of about 0.60, the extruder barrel at its exit end is heatedto about 290 C. to bring said polymer to the desired temperature, andsaid polymer is cooled to about 260 C. at the spinneret.

3. Method of processing the low I.V. fiber of claim 1 comprising (a)feeding the fiber through a water bath heated to about C. with minimumsnubbing;

(b) drafting said fiber about 2.5 to 3:1;

(0) passing said fiber through a steam atmosphere while subjecting saidfiber to a draft tension of about 0.5 gram/denier;

(d) heat setting said fiber at a temperature of about C. to 180 C.; and

(e) cutting said fiber into staple length.

4. Method of claim 3 wherein said fiber is drafted about 2.5 :1 and isheatset at about C. for about five minutes.

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